Temper rolling of steel strip material is used to regulate the mechanical and stiffness properties thereof. Temper rolling results in cold working of the strip material, and is achieved by passing the material through spaced rotating rolls in order to reduce the thickness while maintaining the width essentially constant. The increase in length brought about by reduction in thickness is known as extension, and is one criterion used for determining the relative reduction in thickness.
A tempering mill normally has an input for supplying coiled strip material, spaced apart rotatable work rolls, and an exit or take-up coiling assembly on which the finished product is wound. Control of the extension throughout the length of the strip material is important in order to assure that uniform properties are present. Differential variations in the extension throughout the length of the material can result in unusable product, or product which must be diverted for further processing or the like. One contributor to non-uniform extension is the slip which may occur while the material is being fed through the mill. Although the causes of slip are numerous, good mill control requires that slip be controlled or taken into account, regardless of its source.
The finite length of a coil requires that the mill accelerate the strip material once the coil is loaded, and decelerate the coil after processing is completed. The acceleration and deceleration ranges can occur over a relatively substantial length of the strip material, and it is important that slip be controlled during the acceleration and deceleration phases in order to maximize the percentage of finished material having proper parameters. Should the differential extension during the acceleration and deceleration phases not fall within appropriate ranges, then that material may need to be discarded or further processed.
As noted, the causes of slip are many and it is important that the slip be controlled or taken into account. It is also important that the control system be able to recognize spurious or momentary changes in extension. Should spurious signals not be recognized, then reaction to them could well cause further inaccuracies and result in los of product.
An adaptive control system is one which takes into account the divergence of an achieved result from the expected result. The system adapts to the divergence as a means for compensating for deviation from the expected. Position control may be utilized when the divergence from the desired is fixed, whereas integral control may be used when an average divergence from the desired is known. A combination of integral and position control is one method of assuring that a system is driven toward the desired result.
The disclosed invention is an adaptive control system and method which is advantageously utilized for regulating and controlling extension in a tempering mill. The system continuously monitors the differential extension of the strip material and compares an averaged extension with the aim or target extension as a means for determining the adjustments required. Nine bands of control are provided for driving the averaged extension toward the targeted extension, and each band of control drives the extension toward the target extension with a different degree of intensity. The system includes means for recognizing spurious signals or temporary divergences and disregards those. While the invention is disclosed as utilized with a temperinq mill, those skilled in the art will understand that it may be applied to other mills, both steel and non-steel, wherein slip or some other velocity dependent factor needs to be regulated and controlled.